Preparation And Sodium Storage Properties Of Antimony-based Composite Materials

At present,rechargeable lithium-ion batteries are widely used in electric vehicles and mobile electronic devices because of their high higher specific energy and output voltage,and occupy the rechargeable battery market.However,the prospect of rechargeable lithium-ion batteries is worrying due to the low content of lithium resources in the earth’s crust,different distribution around the world,and rising prices of lithium salts.In recent years,the rapid development of sodium-ion batteries has made many people pay attention to sodium-ion batteries.Because sodium resources are abundant in natural reserves,easy to obtain,low-priced,green and safe,and sodium and lithium are in the same main group.The related physical and chemical properties are very similar,so sodium ion batteries are considered to be a very potential alternative technology.However,the radius of Na⁺is 1.02（?）,the radius of Li⁺is 0.76（?）,the radius of Na is larger than that of Li,and the slow diffusion kinetics of Na⁺,resulting in poor battery performance.Therefore,it is urgent to explore new sodium ion battery materials.There are many anode materials currently being studied.Antimony-based materials are one of the hottest topics for researchers,because the metal antimony（Sb）has a high theoretical specific capacity of 660 m Ah g^-1 and a suitable working voltage（0.5-0.8 V vs.Na/Na⁺）.However,during the charging and discharging process,the volume of the antimony-based material will change drastically（393%）,causing the contact between the antimony-based material and the current collector to become less tight,easily detaching from the conductive network,and losing a lot of battery capacity,which greatly reduces the life of the material.Therefore,phosphate ions and carbon materials were introduced through the method of hydrothermal reaction and surface coating carbon to synthesize composite SbPO₄-C,in which SbPO₄ nanoparticles were coated with conductive carbon.First of all,the larger volume of phosphate ion as a buffer layer alleviates the volume expansion problem of the SbPO₄-C composite material during the sodium insertion and removal process.Second,the carbon protective layer can effectively prevent the structure of the SbPO₄-C composite from collapsing,and at the same time can increase the electronic conduction of the material.Due to the above advantages,the SbPO₄-C composite material exhibits excellent battery performance in sodium ion batteries.At a current density of 0.5 A g^-1,the SbPO₄-C electrode exhibits a capacity of 248 m Ah g^-1 after 200 cycles.the SbPO₄-C electrode can still exhibit a capacity of180 m Ah g^-1 at 1 A g^-1 after 1000 cycles,and its retention rate is 78.3%.Even at 5 A g^-1,there is a capacity of 159 m Ah g^-1.The Na₃V₂（PO₄）₂O₂F||SbPO₄-C full battery also exhibits a high discharge voltage of 3.2 V,showing potential practical application value.More importantly,the conductive carbon coating strategy provides ideas for the design of high-performance rechargeable energy storage devices for other nano-electrode materials.